In an electrophotographic type image forming apparatus, in order to meet various recording materials, an intermediary transfer type is known, in which a toner image is transferred from a photosensitive member onto an intermediary transfer member (primary-transfer) and then is transferred from the intermediary transfer member onto the recording material (secondary-transfer) to form an image.
Japanese Laid-open Patent Application 2003-35986 discloses a conventional constitution of the intermediary transfer type. More particularly, in Japanese Laid-open Patent Application 2003-35986, in order to primary-transfer the toner image from the photosensitive member onto the intermediary transfer member, a primary-transfer roller is provided, and a power source exclusively for the primary-transfer is connected to the primary-transfer roller. Furthermore, in Japanese Laid-open Patent Application 2003-35986, in order to secondary-transfer the toner image from the intermediary transfer member onto the recording material, a secondary-transfer roller is provided, and a voltage source exclusively for the secondary-transfer is connected to the secondary-transfer roller.
In Japanese Laid-open Patent Application 2006-259640, there is a constitution in which a voltage source is connected to an inner secondary-transfer roller, and another voltage source is connected to the outer secondary-transfer roller. In Japanese Laid-open Patent Application 2006-259640, there is description to the effect that the primary-transfer of the toner image from the photosensitive member onto the intermediary transfer member is effected by voltage application to the inner secondary-transfer roller by the voltage source.